1. Field of the Invention
This invention relates to an explosion isolation device for dust collector vessel, and more particularly, to an explosion isolation device that isolates a dust collection drum from a hopper of a dust collector vessel such that dust discharged from the hopper and ultimately deposited into the dust collection drum will not cause an explosion in the dust collector vessel that exceeds the pressure rating of the explosion isolation device and/or the dust collection drum.
2. Background of the Prior Art
Dust collection systems require deflagration isolation (subsonic flame propagation interruption) pursuant to the National Fire Protection Association (“NFPA”). More specifically, Chapter 11, Section 1.1 of the NFPA allows deflagration control by isolation, which pertains to the interruption or mitigation of flame, deflagration pressures, pressure piling, and flame-jet ignition between enclosures that are interconnected by pipes or ducts. Further, chapter 11, Section 1.2 of the NFPA provides that isolation control may be active, which requires the detection, control and response (pneumatic or electrical) to create an isolation barrier; or that isolation control may be passive, which requires a response to a deflagration pressure that generates an isolation barrier. A typical passive isolation control system includes a 55 gallon drum that receives dust discharged from a dust collector hopper.
Prior art active explosion isolation control devices and methods include air lock valves (typically gate valves) disposed between and connected to a bottom portion of a dust collector vessel, and connected to a top portion of a dust receiving container. The gate valve isolates the vacuum pressured dust collection vessel from the dust receiving container to prevent a relatively large quantity of air from entering dust collection vessel through a bottom opening in the vessel when dust is not exiting the vessel, thereby preventing an explosion inside the dust collection vessel that could reach a magnitude that exceeds the burst pressure rating of the dust collection vessel.
The problem with using a valve as an explosion isolation device is that the valve is relatively expensive to purchase and, because of dust accumulation upon the moving valve, relatively expensive to maintain. In the event that the valve is not regularly inspected, the valve can become difficult to operate, which can result in the dust collection system having to be shutdown to implement repairs.
Prior art passive explosion isolation control devices and methods include a 55 gallon drum that has a design pressure that exceeds the design pressure of the dust collector housing. The 55 gallon drum receives dust discharged from a dust collector hopper via a flexible tube or “chute.” When the drum is full, it is transported to a location where the dust can be safely disposed and the drum “recycled” back to the dust collector for refilling.
The problem with prior art passive devices and methods that use 55 gallon drums is that the flexible tube is allows dust to “leak” from the system and become suspended in the surrounding air or become deposited upon the area surrounding the drum. Further, the time and manual effort required to replace a full drum with an empty drum is relative long, arduous and costly.
There is a need for an explosion isolation device and method that is relatively inexpensive to purchase, has no moving parts, that requires virtually no maintenance to keep the device and/or system operational, and that requires a relatively small amount of time and manual effort to dispose of the dust discharged from the dust collector. Further, the device and method must not compromising safety parameters or pressure ratings of a predetermined dust collector vessel or the vessel's cooperating dust collection system.